I see no one wants to play with this one.
Does it have a microprocessor? It might. If it does, that probably uses frequencies above 9 KHz and is required to meet Part 15 standards for digital devices. It's quite possible the manufacturer didn't test it.
If it has a switching power supply, that probably needs Part 15 compliance too. Same caveat.
It doesn't need a switcher if it uses modern, fast-turn-on (and off) control devices. Those'll mess up X-10, big time. There's no real limit on conducted emissions below 150 KHz, and no requirement to check conducted meissions if no onboard clock is 9 KHz or higher, so you will have to deal with the manufacturer on that. However the X-10 folks will be interested!
Every so often, the Consumer Product Safety Commission
recalls electrical items (extension sockets, for example) because they're unsafe, and sometimes even because they have a fraudulent safety compliance mark. Your blanket may have been recalled:
"NEWS from CPSC
U.S. Consumer Product Safety Commission
Office of Information and Public Affairs Washington, DC 20207
FOR IMMEDIATE RELEASE
July 2, 2003
Release # 03-152 Company Phone Number: (877) 882-9478
CPSC Consumer Hotline: (800) 638-2772
CPSC Media Contact: (301) 504-7908
CPSC, Perfect Fit Industries Announce Recall of Electric Blankets
WASHINGTON, D.C. - The U.S. Consumer Product Safety Commission announces the following recall in voluntary cooperation with the firm below. Consumers should stop using recalled products immediately unless otherwise instructed.
Name of product: SOIREE® and Soft n' Warm® Electric Blankets
Units: About 18,000
Manufacturer: Perfect Fit Industries, of Charlotte, N.C.
Hazard: These blankets can overheat, posing a risk of burn injuries to consumers, especially when the blanket is folded or bunched."
"Remedy: Firm is providing a free replacement blanket, but consumers should unplug the recalled units immediately. "
For complete details on this recall, see http://www.cpsc.gov/cpscpub/prerel/prhtml03/03152.html
Finally, even if your blanket has not been recalled, if it produces interference as severe as you describe, you should contact Perfect Fit -- who is responsible for its compliance -- for resolution. You might also send an E-mail to the ARRl describing the problem.
Finally... Ever since the BPL folks started chanting "There are no complaints!" I've been recommending we file online interference complaints with the FCC for EVERY instance of harmful interference we can identify, just so no one else can say "No one complained!"